Flagstaff
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flagstaff clear sky chart from 2005-11-05 to 2017-08-12.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
55%
15453
33%
46540
22%
15412
67%
15412
44%
22988

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
46%
720
31%
2327
21%
716
61%
716
38%
1163
January16th to endNight
44%
768
34%
2496
22%
768
61%
768
35%
1292
February1st to 15thNight
50%
700
32%
2225
23%
700
65%
700
43%
1074
February16th to endNight
39%
632
36%
1889
23%
632
56%
632
37%
979
March1st to 15thNight
45%
720
36%
1980
20%
720
61%
720
45%
1010
March16th to endNight
48%
768
34%
2112
17%
768
63%
768
47%
1064
April1st to 15thNight
36%
686
29%
1945
12%
686
51%
686
39%
988
April16th to endNight
42%
540
41%
1677
19%
540
64%
540
46%
730
May1st to 15thNight
47%
540
35%
1619
20%
539
60%
539
52%
719
May16th to endNight
46%
561
34%
1684
19%
561
59%
561
47%
755
June1st to 15thNight
50%
540
32%
1620
22%
540
59%
540
59%
694
June16th to endNight
68%
540
34%
1620
27%
540
73%
540
65%
674
July1st to 15thNight
73%
510
19%
1530
15%
510
75%
510
41%
824
July16th to endNight
74%
564
17%
1593
15%
531
74%
531
32%
956
August1st to 15thNight
79%
527
26%
1575
22%
524
81%
524
40%
840
August16th to endNight
79%
549
30%
1662
26%
549
81%
549
42%
890
September1st to 15thNight
74%
660
29%
1815
21%
660
78%
660
45%
1011
September16th to endNight
71%
656
42%
1815
27%
656
81%
656
64%
818
October1st to 15thNight
59%
660
38%
1906
22%
660
72%
660
54%
895
October16th to endNight
61%
704
41%
2112
28%
704
73%
704
52%
974
November1st to 15thNight
55%
700
36%
2162
23%
700
70%
700
49%
1015
November16th to endNight
51%
720
38%
2340
27%
720
67%
720
47%
1051
December1st to 15thNight
52%
720
33%
2340
23%
720
67%
720
39%
1162
December16th to endNight
44%
768
30%
2496
23%
768
56%
768
30%
1410

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
342442445%6%57%
47436
Night
221332335%6%64%
46736
TransparencyDay
25%46%19%27%16%
47131
Night
20%37%20%29%18%
46542
SeeingDay
8%20%28%27%11%3
5257
Night
413%21%30%23%6%
15459

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
1324313347%64%
1611
16th to endDay
35%24423346%58%
1728
February1st to 15thDay
16%3341326%7%58%
1637
16th to endDay
142342446%7%58%
1585
March1st to 15thDay
14232235%5%7%60%
1980
16th to endDay
2413313349%61%
2112
April1st to 15thDay
1214434348%60%
2003
16th to endDay
25%23312336%65%
2280
May1st to 15thDay
2423422445%63%
2331
16th to endDay
3223323345%63%
2429
June1st to 15thDay
212212245%75%
2340
16th to endDay
221222333471%
2340
July1st to 15thDay
5%5%247%5%7%7%7%8%39%
2340
16th to endDay
7%6%38%8%47%9%8%9%25%
2467
August1st to 15thDay
8%6%25%7%5%6%6%7%7%37%
2290
16th to endDay
5%425%6%47%8%7%7%40%
2185
September1st to 15thDay
5%426%5%46%6%6%7%44%
1815
16th to endDay
3213322237%67%
1815
October1st to 15thDay
331331333467%
1724
16th to endDay
2212212347%69%
1760
November1st to 15thDay
121222335%5%70%
1696
16th to endDay
3313212225%71%
1620
December1st to 15thDay
25%2442326%7%58%
1620
16th to endDay
25%35%5%35%45%7%51%
1728
January1st to 15thNight
1315%32335%6%62%
2327
16th to endNight
3424323445%60%
2496
February1st to 15thNight
42332235%6%64%
2214
16th to endNight
131342345%7%61%
1889
March1st to 15thNight
1323213447%65%
1980
16th to endNight
1312213347%66%
2112
April1st to 15thNight
1323213447%65%
1945
16th to endNight
11212246%74%
1677
May1st to 15thNight
1112213346%71%
1619
16th to endNight
1212212235%73%
1684
June1st to 15thNight
2112112235%77%
1620
16th to endNight
1221223477%
1620
July1st to 15thNight
32145%35%5%6%8%53%
1620
16th to endNight
43245%47%8%9%12%38%
1701
August1st to 15thNight
333325%6%7%11%51%
1584
16th to endNight
32134345%8%9%54%
1662
September1st to 15thNight
33144245%6%8%56%
1815
16th to endNight
111112245%77%
1815
October1st to 15thNight
21121335%6%71%
1906
16th to endNight
132212245%72%
2112
November1st to 15thNight
121232345%5%67%
2162
16th to endNight
221322334471%
2340
December1st to 15thNight
1324213448%61%
2340
16th to endNight
2436%425%45%6%53%
2496

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
21%37%24%33%9%
1612
16th to endDay
27%37%19%29%11%
1728
February1st to 15thDay
26%37%27%19%16%
1637
16th to endDay
27%36%23%29%10%
1585
March1st to 15thDay
22%4422%33%12%
1980
16th to endDay
21%46%26%28%12%
2112
April1st to 15thDay
22%35%22%32%13%
2003
16th to endDay
22%3319%35%15%
2280
May1st to 15thDay
23%3419%35%15%
2331
16th to endDay
22%3416%37%14%
2432
June1st to 15thDay
12%3211%30%39%
2340
16th to endDay
15%318%27%42%
2340
July1st to 15thDay
36%6%11%13%12%18%
2201
16th to endDay
45%10%16%14%11%1
2312
August1st to 15thDay
41%6%9%15%17%10%
2275
16th to endDay
36%8%10%19%19%6%
2185
September1st to 15thDay
35%6%9%14%16%16%
1815
16th to endDay
18%4317%34%22%
1815
October1st to 15thDay
21%3319%29%22%
1724
16th to endDay
16%2418%38%19%
1760
November1st to 15thDay
16%25%25%32%17%
1696
16th to endDay
17%2421%33%20%
1620
December1st to 15thDay
25%410%26%24%8%
1620
16th to endDay
35%38%23%22%6%
1728
January1st to 15thNight
23%4423%31%11%
2327
16th to endNight
27%35%19%31%13%
2496
February1st to 15thNight
21%37%24%25%18%
2225
16th to endNight
24%36%23%29%13%
1889
March1st to 15thNight
19%3423%36%12%
1980
16th to endNight
17%48%25%31%12%
2112
April1st to 15thNight
20%25%21%35%13%
1945
16th to endNight
13%3422%36%20%
1677
May1st to 15thNight
13%36%25%31%19%
1620
16th to endNight
14%3418%40%17%
1685
June1st to 15thNight
12%1110%30%42%
1620
16th to endNight
10%226%25%52%
1620
July1st to 15thNight
24%6%15%14%17%21%
1530
16th to endNight
31%8%22%19%13%4
1593
August1st to 15thNight
25%6%13%20%22%12%
1575
16th to endNight
23%7%13%22%24%9%
1662
September1st to 15thNight
24%5%11%19%22%16%
1815
16th to endNight
10%3318%35%29%
1815
October1st to 15thNight
15%35%23%28%24%
1906
16th to endNight
15%2416%36%24%
2112
November1st to 15thNight
18%35%23%30%18%
2162
16th to endNight
17%25%19%32%22%
2340
December1st to 15thNight
22%48%26%24%13%
2340
16th to endNight
32%38%23%24%7%
2496

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
10%31%26%22%7%2
90
16th to endDay
6%30%26%21%14%1
96
February1st to 15thDay
7%26%26%26%10%3
152
16th to endDay
16%36%27%15%3
238
March1st to 15thDay
8%27%34%18%8%1
270
16th to endDay
10%26%36%18%5%2
288
April1st to 15thDay
11%33%31%11%9%1
269
16th to endDay
8%42%26%15%41
270
May1st to 15thDay
9%31%34%16%6%1
288
16th to endDay
7%29%30%24%6%1
330
June1st to 15thDay
323%36%23%9%3
315
16th to endDay
39%35%36%13%1
315
July1st to 15thDay
6%8%26%42%13%2
305
16th to endDay
12%414%39%21%7%
327
August1st to 15thDay
9%317%40%22%7%
300
16th to endDay
7%424%36%20%6%
268
September1st to 15thDay
9%8%31%34%13%2
255
16th to endDay
6%14%25%32%14%5%
255
October1st to 15thDay
6%26%26%25%10%4
164
16th to endDay
9%16%31%23%15%3
96
November1st to 15thDay
5%13%28%30%15%6%
90
16th to endDay
8%30%24%28%5%2
90
December1st to 15thDay
416%35%25%14%3
90
16th to endDay
14%25%27%25%6%2
96
January1st to 15thNight
7%14%25%26%16%9%
720
16th to endNight
7%18%25%27%16%5%
768
February1st to 15thNight
416%25%32%17%4
704
16th to endNight
6%22%29%26%12%2
632
March1st to 15thNight
5%19%26%28%15%4
720
16th to endNight
417%26%32%16%2
768
April1st to 15thNight
5%24%27%27%11%2
686
16th to endNight
223%28%28%13%3
540
May1st to 15thNight
217%30%34%13%1
540
16th to endNight
417%26%27%20%3
563
June1st to 15thNight
211%33%33%18%2
540
16th to endNight
1421%41%27%2
540
July1st to 15thNight
5%10%36%40%5%
510
16th to endNight
415%34%44%9%
564
August1st to 15thNight
415%28%49%10%
527
16th to endNight
31431%44%14%
549
September1st to 15thNight
349%27%44%10%
660
16th to endNight
38%13%24%37%10%
656
October1st to 15thNight
410%23%32%22%6%
660
16th to endNight
210%19%32%24%10%
704
November1st to 15thNight
311%25%30%22%5%
700
16th to endNight
5%15%24%27%18%9%
720
December1st to 15thNight
6%15%22%29%22%3
720
16th to endNight
7%16%26%29%14%4
768
Page generated at 2017-08-13 11:16:13. Version ac04

Copyright 2017 A. Danko


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